1. Field of the Invention
This invention relates to a foamable composition comprising a resinous polymer and a mixture of polycyclic aromatic polycarboxylic acids derived from a carbonaceous material, such as coal.
2. Description of the Prior Art
Foamed resinous polymers, such as thermoplastic or thermosetting polymers, are of significant commercial interest, because they are lightweight and relatively inexpensive, have excellent chemical stability and are easily fabricated into a wide variety of useful articles, such as insulated containers for cold foods, buoyant fillers for life preservers, toys, disposable coffee cups, etc.
In a typical foaming process, the foaming agent is admixed intimately with the resinous polymer and the mixture is heated in a mold above the decomposition temperature of a foaming agent, whereupon the foaming agent decomposes to yield gaseous products which cause the polymer to foam. Thereafter the polymer is cooled and retains its foamed configuration.
Desirably, the foaming agent should be inexpensive, mix well with the resinous polymer, provide sufficient and controllable foaming power and should have no residual adverse effect upon the equipment used during the foaming step or on the resulting foamed polymer.